Here's your plugin. Just go to Tools > New Plugin. Paste this into the new file. Save the file as whatever you want (I called it HighlightUnsaved.py), just make sure you save it in your User folder in Sublime Text's Packages directory (should be the default when you press save as but I'm not positive).

Interesting approach.How I understand the API that is not possible to intercept an event before the user changes the contents of a row to save its state and compare it after each change to see if it was restored to its original state.An alternative might be to save all rows in a buffer when the file is loaded (but consume a lot of memory) and use that for comparison instead of opening the original file for each change.The problem with the comparison between the original file or a buffer is that the addition of a line means that all subsequent lines will appear to be changed.Anyway thanks for this code!

I'm new to Python/Plugin Development so there is probably a better way to make the plugin. This way was the first way that I thought of. The addition of new lines will cause trouble to the plugin... and I can't seem to think of a workaround that wouldn't take a lot of memory. (I didn't realize you'd be judging my code so much )